Theoretical study of time delays in (w; 2w) above threshold ionization

LÓPEZ, S. D.; DONSA, S.; S NAGELE; J. BURGDÖRFER; ARBÓ, D. G.

Budapest

Conferencia; The International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces; 2018

Experiments employing either attosecondstreaking or the complementary interferometricRABBIT technique have allowed to study photoemissionfrom rare gas atoms and surfaces inthe time-domain with attosecond precision. Theexperimental progress has triggered considerabletheoretical eorts to understand photoionizationfrom a time-dependent perspective (see [1] andreferences therein).The experiment in atomic ionization by twocolor(!; 2!) lasers by Zipp et al. [2] has revealedthat a pump-probe scheme can be used to characterizetime delays in the emission of electrons inthe above-threshold ionization regime for visiblefrequency of the pump. In this work, we performa theoretical analysis of the time delays inAr ionization by two-color laser for a typically(!; 2!) conguration of Ti:sapphire laser (800nm). To shed more light in ionization processwe perform simulations with the time dependentSchrodinger equation and compare this resultswith the strong eld and Coulomb-Volkov approximations.We nd that time delays dependon the denition from electron momentum distributions.Besides, we also nd a large discrepancybetween the results predicted by the strong eldapproximation (zero delay for sidebands) and numericalsolutions of time-dependent Schrodingerequation at the highest simulation energies. Wealso nd that the strong assumption of additivetime delays adopted in streaking or RABBITTtechniques [3] needs to be revisited when appliedto the case of (!; 2!) lasers due to the multiplicityof coherent quantum paths leading to a nalmultiphoton peak. Finally, we explore simplerquantum paths to get a better understanding ofthe process. For this purpose we use Yukawapotentials tting the electron binding energy toallow the absorption of a desired number of photonsto reach the continuum. This analysis pavesthe way to understand the process and the timedelays asociated to each path.As an example, we show in Fig. 1 timedelays obtained from asymmetries and forwardemission, considering integrations over z hemispheres.Figure 1. Delays calculated as a function of theemission energy for sidebands within the TDSE.The delays are calculated for forward emission (triangles)and asymmetry (circles). The calculationswere performed integrating around peak energy(solid symbols) or considering only the peak energy(open symbols). The 2! component intensityis 8 1013 W/cm2 and the ! component is41011 W/cm2.This work was supported by the FWFAustria(SFB NEXTLITE, SFB VICOM),by CONICET (PIP100386), by ANPCYT(PICT-2016-0296 and PICT-2016-3029), by theOeAD (WTZ AR 03/2013), by the NSFthrough XSEDE resources (TG-PHY090031),and through computational resources at the ViennaScientic Cluster (VSC).References[1] R. Pazourek, S. Nagele, and J. Burgdorfer, Rev.of Mod. Phys., (2015), 87, 765 .[2] L. J. Zipp, A. Natan, and P. H. Bucksbaum, Optica,(2014) 1, 361-364.[3] J. Feist, O. Zatsarinny, S. Nagele, R. Pazourek,J. Burgdorfer, X. Guan, K. Bartschat and B. I.Schneider, Phys. Rev. A, (2014), 89, 033417.